Çум тăваткĕтеслĕх
Çум тăваткĕтеслĕх — çавракăшăн сĕртĕневĕшĕсен тăсăмĕсенчен пулнă тăваткĕтеслĕх.

Вуламалли 
 Alexander Bogomolny. Accessed 2011-08-18 Inscriptible and Exscriptible Quadrilaterals // Interactive Mathematics Miscellany and Puzzles. — 1995.
 Martin Josefsson. Similar Metric Characterizations of Tangential and Extangential Quadrilaterals Forum Geometricorum. — 2012. — Т. 12.
 Mowaffaq Hajja. A Very Short and Simple Proof of “The Most Elementary Theorem” of Euclidean Geometry // Forum Geometricorum. — 2006. — Т. 6.
 Kiran S. Kedlaya. Geometry Unbound. — 2006.
 Mirko Radic, Zoran Kaliman, Vladimir Kadum. A condition that a tangential quadrilateral is also a chordal one // Mathematical Communications. — 2007. — Вып. 12.

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